These studies will utilize organ cultures of embryonic rat and chick lung tissues to study extracellular matrix synthesis, and the role of the matrix components in regulating bronchial development. The types, relative proportions and organization of collagen, proteoglycans, and basement membranes synthesized in developing lung tissues will be determined, and the cells synthesizing these macromolecules will be identified. Since the interstitial matrices and the interface of bronchial mesoderm and epithelium are always intimately associated with a basement membrane, a special emphasis will be placed on the synthesis and deposition of basement membrane components. Characterization of the extra-cellular matrix components will be done with transmission and scanning electron microscopy, autoradiography, immunochemical staining, and biochemical analyses. In addition, we will study the effects of microenvironmental variables such as tissue oxygen levels, exogenous macromolecules, and various pharmacological agents on extracellular matrix synthesis and bronchial morphogenesis. These studies will contribute to our understanding of (1) the regulation of lung development, (2) the role of extracellular matrices in the maintenance of airway shaped and (3) the effects of conditions such as hypoxia on connective tissue matrix synthesis in developing lung tissues.